Each VLAN in the network required a unique IP subnet because two devices in the same VLAN with different subnet addresses, cannot communicate. During the VLAN configuration this a common problem, and we can solve this problem by identifying the incorrect IP address configuration and changing the address to the correct one. For example, if you want to connect a client anywhere in the VLAN 10 then you must require a valid subnet configuration. If you want to communicate outside the VLAN you must require valid default gateway. The default gateway must be the VLAN 10 SVI address. In the figure below, the PC-2 cannot connect to PC-3 and PC-4, but PC-3 and PC-4 can communicate each other.
A check of the IP configuration settings of PC-2 shown in figure-2, Reveals the most common error in configuring VLANs a wrongly configured IP address. PC-2 is configured with an IP address of 18.104.22.168, but it should have been configured with 192.168.20.1.
Change the PC-2 IP address to correct IP address 192.168.20.1. The PC-2 Ethernet configuration now shows the updated IP address of 192.168.10.1. The Figure below illustrates the output on the bottom reveals that PC-2 has regained connectivity to the Web server found at IP address 192.168.20.1.
SVI is standing for Switched Virtual Interface. It is routed interface in IOS representing the IP addressing space for VLAN connected to this interface. The VLAN has no physical interface so; the SVI provides Layer 3 processing for packets from all switch ports associated with the VLAN. With this interface switch uses virtual layer 3 interfaces to route traffic to another layer 3 interfaces which eliminate the need of the physical router. For virtual intereface configuration, ensure your switch has a VLAN represented by the SVI you want to create. The command are following: